Distributions of endogenous hormones relative to formation of cracked and malformed fleshy roots of carrots

Endogenous hormones (an important internal factor) promote fleshy root thickening in carrot by controlling root sink activity, however, it is not entirely clear whether the distribution of endogenous hormones is related with the formation of cracks and deformities in fleshy root of carrots. The distributions of endogenous hormones across transverse section and along longitudinal section of normal, cracked and deformed fleshy root of carrot (“Qishantouxinhong”) were investigated using the ELISA method. The relationship between the endogenous hormones contents and formation of cracked and malformed flesh roots of carrots was discussed. The results showed that GA₃, GA₄, ZR, DHZR and IAA contents in the outer and mid-outer transverse sections of cracked fleshy roots of carrots were lower than those in the other parts of the plant during the fast metaphase stage of root thickening. Also the contents of GA₃, GA₄, ABA and IAA in outer and mid-outer transverse sections of cracked fleshy root of carrots were lower than those in the other parts of the plant during the fast telophase stage of root thickening. Compared with outer-dominance in normal fleshy roots, endogenous hormone distribution was dominant in the inner and middle vertical cross-sections of cracked fleshy root carrots. This could have led to the formation of cracks in fleshy root carrots. Also compared with top/end-dominance in normal fleshy root carrots, the distributions of GA₄, ZR and DHZR contents exhibited an end-dominance along the longitudinal cross-sections of cracked fleshy root of carrots. In fact, GA₃, ABA and IAA exhibited even distributions in malformed fleshy root of carrots during the fast root thickening stage. The analyses showed that variations in the distributions of endogenous hormones resulted in deformities fleshy root of carrots.